Police have removed and arrested two men who locked themselves to the axle of a truck on Olympic Way, blocking the road for more than four hours.

The men were among a group of about 30 of the activists that stormed the road with their symbolic lizard car to create a block about 8.20am.

Many of the stranded vehicles were able to turn around but protesters stormed one truck, jumping on it and hanging banners from the front and back.

Two of the activists locked on to the truck's axles using specially made 'V' locks. The lock loops over the axle and an arm is locked into each end of the 'V'.

Police also arrested two protesters, a man and a woman, for disobeying police orders to move off the road.

About 50 police officers moved in to push the protesters off the road. A tow truck was brought in to remove the lizard car and temporary fencing was erected around the truck as police worked to remove the two men.

Once the two men were removed and arrested about 11.30am, the protesters continued to sit on the side of the road.

Police allowed them to stay for about half an hour, before they issued a warning they would be arrested for loitering and started pushing them back to their camp.

Three were arrested for refusing to go.

One of the protesters who chained himself to an axle said "desperate people do desperate things".

"This world has just about had enough of being pillaged by multi-national companies," he said.

"It's time for it all to stop and it starts right now."

Truck driver Peter Levy, of Northern House Transport, said the protesters had rights to share their voice but this direct action came as a surprise.

Activists critical of police at mine

Anti-nuclear activists have criticised the tactics of police during their five days of protest at the Olympic Dam uranium and copper mine in South Australia's north.

Most of the activists left the area on Wednesday and organisers declared the event a success, with people coming from all states as well as Japan, Canada and Europe.

'However, we are extremely disappointed by the tactics of police, which have included barricading us into our camp, constant surveillance and spotlighting by helicopter, motorbikes and patrol cars 24 hours a day,' spokeswoman Nectaria Calan said in a statement on Thursday.

'With close to a one-on-one ratio of protesters to police it is hard to understand how the state can justify this excessive deployment of resources.'

Thirteen people were arrested at Olympic Dam over the five days with police and protesters clashing twice on Tuesday.

In the second incident, seven people were charged with failing to obey a direction when they staged a cricket match on a road, blocking traffic.

Ms Calan said the police response to that incident had been 'heavy handed'.

But police said each time arrests were made the activists had been allowed to occupy roads for a reasonable period before being asked to move.

The estimated 350 people who gathered at Olympic Dam want to stop the $30 billion expansion of the project which will create the the world's largest open cut mine.

Annual copper production will triple to about 750,000 tonnes and uranium oxide production will jump to 19,000 tonnes.

BHP Billiton has until the end of the year to give the expansion the final go-ahead or face having to renegotiate approvals with the state government.

The protest at Olympic Dam followed court action by Aboriginal elder Kevin Buzzacott who also wants to block the mine's expansion.